Electric gaseous discharge device of the metal vapor type



Oct. 6, 1936.

C. E. FENWICK ET AL ELECTRIC GASEOUS DISCHARGE DEVICE OF THE METAL VAPOR TYPE Filed Sept. 27, 1954 INVENTORS atented has. 6, i936 aotaese lEHrlEiDTlRiliC GASEKNUS DESGHARGTE lllllEVlICE (INF METAL VAIPQ'NRI TYPE New York Application September 2?, 193%, Serialblofiilddld lln Great Britain @ctober lit, with 3 @ilaime.

The present invention relates to electric gaseous discharge devices of the metal vapor type, and particularly to the use of such devices in combination with incandescent lamps.

A particular object of the invention is to provide an illuminating unit containing both an incandescent lamp and a metal" vapor arc lamp. A fur ther object of the invention is to provide means whereby the incandescent lampcan be located in proximity to the vapor'arc device. Another object of the invention is to provide a novel ven= tilating arrangement for an illuminating unit. Still other objects and advantages of the inven= tion will appear from the following detailed speciiication or from an inspection of the accompanying drawing.

Ihe invention consists in the new and novel combination of elements which is hereinafter set forth and claimed.

For some purposes, as where a close approrzi= mation of daylight is desired, it has been found advantageous to combine an incandescent lamp with a metal vapor arc lamp within a single fixture. For example, the combination of a mer cury vapor arc lamp with an incandescent lamp has been found to give an exceptionally pleasing light. In many cases it is desirable to use the recently developed high intensity type of mercury vapor arc lamp, such as disclosed by Francis in his Patent 1,948,261, granted February 20, 1934, both because of its extremely high emciency and because itscompactness greatly simplifies the problem of combining it in a suitable fixture with the incandescent lamp. In practice several incandescent lamps are usually placed symmetrically around this vapor arc lamp in order to obtain a uniform light distribution. An enclosure, which consists normally of either a metal frame work containing panels of diffusing or mottled glass, or any other suitable type of enclosing globe, is provided around this composite light source, both for the purpose of'weather protection and to better intermix the light from the difierent sources. With this arrangement, however, we have found that it is extremely difilcult to restart the mercury vapor are if the light unit is only momentarily switched off for any reason. In fact, in some cases it is impossible to restart the mercury are at all under these conditions. This difiiculty is due to the fact that the arc is self-initiating in this type of device only at a relatively low vapor pressure. In the absence of the incandescent lamps, therefore, the lamp cools after being extinguished, until this lower vapor pressure is reached, whereupon the arc is auto- (Cll. Zib dhlli matically reinitiated, provided that operating potential is still applied thereto. But where incandescent lamps are located in proximity to the arc lamp, as in the present case, these lamps restart as soon as the potential is reapplied, and

the heat therefrom materially decreases the rate of cooling of the mercury vapor arc lamp and thus increases the time interval before it will restart. In some cases, where the illuminating unit is exceptionally compact, this heating by the incandescent lamps has been found to be sufiicient to maintain the mercury vapor arc lamp above its restarting temperature, so that restarting of the mercury arc could be attained only by extinguishing the incandescent lamps for an appreciable period.

We have now discovered that these dimculties are entirely eliminated, regardless of how closely the incandescent lamps are placed with respect to the high intensity mercury vapor arc lamp, by providing means to reduce the heat transfer from the incandescent lamps to the mercury arc lamp. In a practical device which we have de veioped this means takes the form of a glass chimney about the mercury vapor arc lamp, by means of which the arc lamp is shielded from convection currents produced by the incandescent lamps. This chlmney likewise results in a flow of cool air over the mercury vapor are lamp, due not only to the heating of this alr by the mercury vapor arc lamp itself, but also because of the suction eifect of the convection currents produced by the incandescent lamps. Withthis novel structure we have been able to produce an extremely compact and eiiicient light source employing both a high intensity mercury vapor arc lamp and incandescent lamps, which will restart in an entirely satisfactory manner under all conditions.

For the purpose of illustrating our invention we have shown a somewhat schematic, crosssectional elevation of a preferred embodiment thereof in the accompanying drawing.

As shown in this drawing the high intensity mercury vapor arc lamp i is surrounded by a chimney 2 of any suitable transparent or translucent glass which is capable of withstanding the somewhat elevated temperature produced by the lamp. This chimney is suspended below a vitreous enamel reflector 3 by three rods t having suitable lugs 5 at the bottom which engage the lower edge of said chimney. In those cases where it is desired it is also contemplated that this chimney should be made of one of the well known heat or infra-red absorbing glasses, by means of which the heat received by the lamp from the incandescent lamp is further reduced. A plurality of incandescent lamps 6 are symmetrically arranged around said chimney 2, and enclosing this comlong as it is operating. After it is extinguished,

however, it .must cool sufiiciently to reduce the vapor pressure therein before it will again start itself into operation. In the case of a momentary extinguishment of the unit, due to a power failure or to an unintentional operation or the controlling switch, for example, the incandescent lamps 6 immediately light up, once the potential is again applied, and the heat therefrom would greatly delay, if not entirely prevent the necessary cooling of the lamp, it it were not for the presence of the chimney 2. This chimney, however, not only shields the lamp i from the convection currents caused by the lamps 6, but also results in a constant flow of cool air over the lamp i which materially hastens the cooling thereof, and thus results in a more rapid reinitiation oi the arc insaid lamp.

While we have illustrated our invention by reference to a particular embodiment employing incandescent lamps it is obvious that other types of lamps, including some of the gaseous discharge devices, such as a. neon lamp, can be used in place thereof, the same problems being there involved. It is also to be understood that various other omissions, changes and substitutions, within the scope of the appended claims, may be made therein withoutdeparting from the spirit of our invention.

What we claim asnew and desire to secure by Letters Patent of the United States is:--

1. In combination, a vapor discharge lamp in which the discharge is self-starting only below a given vapor pressure, another lamp which emits light as soon as potential is applied thereto in proximity to said first mentioned lamp, and means to prevent the circulation of heated air from the latter of said lamps past the former when only the latter is in operation in order to facilitate the restarting of said discharge.

2. In combination, a vapor discharge lamp in which the discharge is self-starting only below a given vapor pressure, another lamp which emits light as soon as potential is applied thereto in proximity to said first mentioned lamp, and a chimney surrounding said vapor discharge lamp and separating it from the other lamp, and means independent of said chimney to permit the escape of hot air from about the latter lamp.

3. In combination, a vapor discharge lamp in which the discharge is self-starting only below a given vapor pressure, another lamp which emits light as soon as potential is applied thereto in proximity to said first mentioned lamp, an opening thereabove for the escape of heated air, and means comprising a chimney about said discharge lamp which separates it from the other lamp and extends up into the path of convection currents above said other lamp, whereby the operation of the latter lamp increases the flow of cool air over said discharge lamp to facilitate the reinitiation of a discharge therein.

CHRISTOPHER E. FENWICK. LEONARD J. DAVIES. EDWARD 3., 'IUPPEN. 

